In many devices employing a camera, cell phones in particular, the camera is provided as a module, consisting of one or more lens elements and an imaging IC, all enclosed in a housing. Due to the tight space requirements, cell phone cameras are a fixed-focus variety—there is simply not enough room for a conventional, mechanical focusing system. Besides focusing abilities, cell phone cameras will eventually include optical zoom, which is not feasible given conventional optical systems and space requirements. Other applications where a compact camera is desirable include endoscopes, borescopes, personal digital assistants (PDAs), and vehicular collision avoidance cameras.
An electroactive lens is a single optical lens element that changes its focal length in response to an applied voltage. Two varieties of electroactive lenses include the liquid lens and the liquid crystal lens. In contrast, conventional optical systems change focal length by mechanically repositioning two or more fixed focal length lens elements relative to each other. Electroactive lenses are more compact and consume less power. Electrically, electroactive lenses can be modeled as a capacitor.
Electroactive lenses offer the promise of providing focusing, and eventually zooming, in a compact module. To minimize space and to provide drop-in design, it is also a goal to incorporate the lens driver inside the camera module. Complicating the situation is the fact that space inside a camera module is minimal, comprising of space around the periphery of the imaging IC.